The invention belongs to the technical field of pharmacy, and in particular relates to a preparation method of nimodipine, comprising urethane reaction and cyclization reaction, wherein in the urethane reaction, after ammonia introducing reaction, adding an inorganic salt for dewatering the urethane reaction liquid, then rectifying to obtain isopropyl-3-aminocrotonate; and performing cyclization reaction with 2-(3-nitrobenzylidene)-acetoacetic acid-2-methoxyethyl ester by taking fatty alcohol as a reaction solvent. The invention has the advantages of high product yield and good quality, the primary yield can reach 85-89%, the solvent can be recovered for use, the raw material cost can be greatly reduced, and the content of total impurities is decreased from 0.4-1.0% of the original process to 0.1-0.3% by HPLC (High Performance Liquid Chromatography) detection.